Sökning: "Rare species"

Visar resultat 21 - 25 av 142 avhandlingar innehållade orden Rare species.

1. 21. Community Robustness Analysis : Theoretical Approaches to Identifying Keystone Structures in Ecological Communities

   Författare :Sofia Berg; Tomas Jonsson; Bo Ebenman; Daniel Stouffer; Linköpings universitet; []
   Nyckelord :;

   Sammanfattning : Most of the world’s ecosystems suffer from stress caused by human activities such as habitat destruction, fragmentation, overexploitation of species and climate change. These factors affect the reproduction and/or survival of individual species as well as interactions between species in ecological communities. LÄS MER

3. 22. Mechanisms and mediators of apoptosis : with special reference to hematological disorders

   Författare :Bengt Fadeel; Karolinska Institutet; Karolinska Institutet; []
   Nyckelord :apoptosis; Bcl-2; caspases; chemotherapy; chronic granulomatous disease; familial hemophagocytic lymphohistiocytosis; Fas; homology-based modeling; neutrophils; phosphatidylserine; reactive oxygen species;

   Sammanfattning : Life and death are inextricably entwined. Naturally occurring cell death or apoptosis is essential for the of homeostasis and serves to remove extraneous or dangerous cells in a swift and unobtrusive manner. work has demonstrated that such cell death is genetically regulated and transpires according to evolutionarily conserved pathways. LÄS MER

4. 23. Genetic variation, clonal diversity and breeding system in sedges (Carex)

   Författare :Olle Jonsson; Biologiska institutionen; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Systematic botany; Carex ericetorum; Carex caryophyllea; Carex bigelowii; Carex arenaria; phenology; niche; genet identification; clone size; isozyme; gene flow; introgression; allozyme; gene diversity; population genetics; taxonomy; morphology; phytogeography; chemotaxonomy. Physiology of nonvascular plants; Systematisk botanik; taxonomi; morfologi; kemotaxonomi. Växters fysiologi inte kärlväxter .;

   Sammanfattning : In this thesis I investigate genetic variation in clonal plants within the wind-pollinated plant family Cyperaceae and, in particular, in species of Carex. Clonal diversity and the spatial distribution of clones (genets) within populations was investigated in Carex bigelowii (in Iceland and Scandinavia) and C. LÄS MER

5. 24. Island biogeography of young land uplift islands - viewed through the lens of bryophytes in a northern Swedish archipelago

   Författare :Andreas Karlsson Tiselius; Mats Dynesius; Roland Jansson; Göran Englund; Joakim Hjältén; Tord Snäll; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; functional data analysis; metacommunity; isolation; mosses; liverworts; sporophyte production; dispersal-establishment trade-off; ekologisk botanik; Ecological Botany; Conservation Biology; naturvårdsbiologi; Statistics; statistik;

   Sammanfattning : Increasing habitat fragmentation and rapid global warming is changing the conditions for species populations and ecological communities around the world. This presents challenges for the maintenance of biodiversity and a dominant paradigm for conservation in fragmented habitats is given by island biogeography and metapopulation (or metacommunity) ecology. LÄS MER

7. 25. Rarity in boreal stream: patterns, causes and consequences

   Författare :Per-Ola Hoffsten; Bo W. Svensson; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Ecology; Central Sweden; site occupancy; dispersal limitation; natural disturbances; recolonization; flight-morphology; metapopulation; habitat stability; spring specialists; Crunoecia irrorata; niche limitation; Isogenus nubecula; nestedness; longitudinal distribution; Ekologi; Terrestrial; freshwater and marine ecology; Terrestisk; limnisk och marin ekologi; zooekologi; Animal Ecology;

   Sammanfattning : Patterns of site occupancy among boreal stream insects were studied in central Sweden with focus on sparsely distributed species and the role of dispersal and niche limitations.In the study of dispersal limitation, I found that effects of an extraordinarily harsh winter in small to medium-sized streams were strongest in sites located in small streams and far from lake outlets. LÄS MER